Hello,

We use a linux box for routing and traffic shaping (we have a few thousand ip addresses routed through this box) and the soft interrupt load is very high.
We use linux kernel 2.6.32.7 on an Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz.
Cpu1 serves an internal network interface, and Cpu3 serves a single physical network interface (with 2 vlans):
Cpu0 : 0.4%us, 0.0%sy, 0.0%ni, 98.2%id, 0.0%wa, 0.0%hi, 1.4%si, 0.0%st
Cpu1 : 0.7%us, 0.0%sy, 0.0%ni, 16.1%id, 0.0%wa, 0.3%hi, 82.9%si, 0.0%st
Cpu2 : 0.0%us, 0.0%sy, 0.0%ni, 96.1%id, 0.0%wa, 0.0%hi, 3.9%si, 0.0%st
Cpu3 : 0.0%us, 0.0%sy, 0.0%ni, 18.2%id, 0.0%wa, 0.7%hi, 81.2%si, 0.0%st
Mem: 2051812k total, 816388k used, 1235424k free, 134232k buffers
Swap: 6016300k total, 0k used, 6016300k free, 110356k cached

Cpu0 and Cpu2 are idle most of the time.

Is there any way to use multiple processors to handle software interrupts for the same network interface, so that the load be distributed across multiple processors ?
Any other suggestions to ease the load are welcome.

Thank You !

Bogdan-Florin Florea

how are you routing the addresses, using something like iptables in linux or an app on top of linux. from what i understand - it seems that the app or the internal system calls arent multi-threaded per physical interface. perhaps the app itself was written to only use a maximum of two proc cores. if a software fix isnt possible then maybe you can somehow split the network traffic into two parts - and run two instances of the program/iptables and dedicate each to a set of cores.
general outline:


input-->spliter-->{routing instance A and B}-->combiner-->output


doing something like this would be a band-aid and not a long term solution - which would be to accurately load share across the cpus natively.